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POPULAR SCIENCE REVIEW. 
in lofty folds. The continuity of the outer division of the en- 
velope is broken by numerous round or oval openings of various 
sizes, sometimes very large, which allow a free ingress of the 
water to the space just beneath. These are the afferent ostioles, 
through and into which a constant current of floating particles 
may be seen moving with considerable vivacity. Here and 
there, scattered at wide distances, finger-like hollow processes 
from the outer division arise singly and at various angles. 
Each is terminated by a large aperture, the efferent ostiole , 
from which a current of water and floating matter emerges with 
more or less spasmodic irregularity. The smaller individuals, 
from half a line to half an inch in diameter, possess only one 
such osticle, and those an inch in diameter seldom have more 
than two or three like conduits ; but they are very large, some- 
times a quarter of an inch in length, and of the proportions and 
taper of the human forefinger.” Focussing lower shows the 
inner division pierced with more numerous openings, 44 smaller, 
methodically arranged, and each one corresponding to, and 
overlying a hollow group of monads.” These monads, or 
44 monad-cephaloids,” are the chief objects to be considered. 
They are described as found in 44 deep spherical hollows,” or 
44 monad chambers,” mere cavities without lining walls. The 
monads are stated to be 44 not cells but heads of a polycephalic 
individual,” corresponding functionally to the tentaculated 
heads of polyps. Each monad chamber has a single small 
circular aperture, which perforates the inner investing membrane 
and allows egress into the circulatory apartment. The aperture 
varies in size at times, and may be completely closed.” The 
monads are arranged 44 radiatingly from and about the centre,” 
and the interior of the cavity appears filled by a collection of 
vibrating bodies, an effect arising from their ciliation. The 
converging bodies are, we are told, soon recognised to be 
craspedote * flagellate monads, so closely packed together, side 
by side, as to form a continuous stratum.” 
These monads Professor Clark finds very similar to those he 
found in Leucosilenia , and like those described by Carter in 
Grantia compressa. Each one has a single flagellum or whip 
filament. 44 The body proper of a cephaloid is a little shorter 
than it is broad ; on the whole spheroidal in shape. Its poste- 
rior end is broadly rounded, and so is its anterior extremity. In 
front rises a cylindrical membranous collar, which tapers 
slightly and projects forward to a distance equal to considerably 
more than twice the length of the body.” The flagellum rises 
from the anterior end of the body, and looks like a black thread. 
There are in the body of the monad two or three clear spots 
* From the Greek kraspedon , an edge or border. 
